In the prior art:
U.S. Pat. No. 95,938 discloses an oval or elliptically shaped door member which is pivoted about a transverse axis and when opened intersects and presents an obstruction in the flow path through the opening.
U.S. Pat. No. 2,136,289 discloses a circularly shaped window constructed with two half disc segments where one of the segments is rotatable in a casing frame. The window is not intended to function as a hatch closure member.
U.S. Pat. No. 2,156,110 discloses a cover for use with a thin material where a cover plate utilizes spring members to retain the cover plate in an opening. This is a snap type of cover.
U.S. Pat. No. 2,363,454 discloses a cabinet with an elongated frame opening. A circular door member rolls into and out of a closing position with respect to an opening.
U.S. Pat. No. 2,480,692 discloses a cover which utilizes notches for release of a cover plate in a given rotative position of the cover plate and springs for retaining the cover plate in an opening.
German Pat. No. 705,897 issued May 13, 1941 discloses a segment window construction in which manipulation of a member can be employed to remove a segment from a seated condition through an opening.
French Pat. No. 2,396,862 issued July 5, 1977 shows a removable door structure which has manipulation space available to remove the door.
Previous hatches used in space vehicles were either closed in a semi permanent way or closed with a mechanism that forced the hatch against its seals. The semi permanent approach did not provide the capability to quickly open or close the hatch since around their perimeter they contained a series of bolt type fasteners that had to be actuated individually and prevented the hatch from being realistically opened by a crewman on the opposite side. The hatches that were closed with a mechanism were very elaborate in that the systems consisted of a large number of mechanical linkages all activated simultaneously to move levers around the periphery of the hatches. This mechanism had to be operable from either side of the hatch which required a penetration of the hatch with a moving part that required positive sealing at the penetration.
The proposed hatch does not have any moving latches or levers, or penetrations with moving parts,, requiring seals, in that it uses the pressure differential across the hatch to force the hatch against its "O" ring seals. The lip seal acts as a gas barrier during pressurization which forces the hatch against the mating "O" ring sealing surfaces. This hatch can be used to seal against a pressure differential in either direction since it is designed to seal on either side partially reducing the number of hatches required. It is also operable from either side by a single person and cannot be opened with a pressure across it where others have this potential hazard. Since this design consists of few parts its recurring cost potentially less and its reliability is greater than the mechanically actuated earlier designed hatches. It is also more versatile than the fixed hatches in that it allows the crewman to operative it quickly.
This hatch design has the additional advantage as an Extra Vehicular Hatch of opening outward and yet using internal vehicular pressure to force it to seal. By opening outward it requires practically no internal sweep volume there by allowing the airlocks to be shorter reducing depressurization/repressurization times. this reduces crew idle time and pumping power requirements.